Influences of Anisotropy on Shale Brittleness Evaluation

Abstract Shale brittleness is one of the most important parameters to assess how the shale behaves upon subjecting to applied stress and evaluate the hydraulic fracturing treatment. Presence of lamination is a common feature in organic-rich shales which significantly create anisotropy in elastic properties and rock brittleness due to the platy minerals such as clays that have the tendency to be aligned in parallel orientation during burial and the digenesis process. Characterization of anisotropy and the understanding the controlling factors on the reservoir rock elastic properties, rock strength and rock brittleness are crucial for successful production and development of shales. The objective of this paper is to extend the previous discussion by (Ibrahim et al 2019), in which an integrated approach has been developed for evaluating the shale fracability, to explain the influences of shale lamination and emphasize on the effects of anisotropic in elastic properties on brittleness of organic-rich shales to better demonstrate the process of screening hydraulic fracturing candidate intervals and improve the hydraulic fracturing design which can eventually improve the production forecast. In this paper, we propose the vertical transverse isotropic (VTI) modeling to investigate the effect of shale lamination and anisotropy on rock elastic properties, tensile failure and wave velocity normal to bedding plane, which differ than they are when parallel to bedding plane. Throughout this study, it is observed that there is a remarkable effect of anisotropy parameters on rock elastic properties and tensile failure. This method help obtain more accurte brittleness index and give precise guide to optimize perforation depths choice and hydraulic fracturing design that can result in optimized hydrocarbon productivity.